Lectures on Evolution | Page 6

between sea and land, The river-horse and scaly crocodile.
At once came forth whatever creeps the ground, Insect or worm."

There is no doubt as to the meaning of this statement, nor as to what a
man of Milton's genius expected would have been actually visible to an
eye-witness of this mode of origination of living things.
The third hypothesis, or the hypothesis of evolution, supposes that, at
any comparatively late period of past time, our imaginary spectator
would meet with a state of things very similar to that which now
obtains; but that the likeness of the past to the present would gradually
become less and less, in proportion to the remoteness of his period of
observation from the present day; that the existing distribution of
mountains and plains, of rivers and seas, would show itself to be the
product of a slow process of natural change operating upon more and
more widely different antecedent conditions of the mineral frame-work
of the earth; until, at length, in place of that frame-work, he would
behold only a vast nebulous mass, representing the constituents of the
sun and of the planetary bodies. Preceding the forms of life which now
exist, our observer would see animals and plants, not identical with
them, but like them, increasing their differences with their antiquity and,
at the same time, becoming simpler and simpler; until, finally, the
world of life would present nothing but that undifferentiated
protoplasmic matter which, so far as our present knowledge goes, is the
common foundation of all vital activity.
The hypothesis of evolution supposes that in all this vast progression
there would be no breach of continuity, no point at which we could say
"This is a natural process," and "This is not a natural process;" but that
the whole might be compared to that wonderful operation of
development which may be seen going on every day under our eyes, in
virtue of which there arises, out of the semi-fluid comparatively
homogeneous substance which we call an egg, the complicated
organisation of one of the higher animals. That, in a few words, is what
is meant by the hypothesis of evolution.
I have already suggested that, in dealing with these three hypotheses, in
endeavouring to form a judgment as to which of them is the more
worthy of belief, or whether none is worthy of belief--in which case our
condition of mind should be that suspension of judgment which is so
difficult to all but trained intellects--we should be indifferent to all a
priori considerations. The question is a question of historical fact.
The universe has come into existence somehow or other, and the

problem is, whether it came into existence in one fashion, or whether it
came into existence in another; and, as an essential preliminary to
further discussion, permit me to say two or three words as to the nature
and the kinds of historical evidence.
The evidence as to the occurrence of any event in past time may be
ranged under two heads which, for convenience' sake, I will speak of as
testimonial evidence and as circumstantial evidence. By testimonial
evidence I mean human testimony; and by circumstantial evidence I
mean evidence which is not human testimony. Let me illustrate by a
familiar example what I understand by these two kinds of evidence, and
what is to be said respecting their value.
Suppose that a man tells you that he saw a person strike another and
kill him; that is testimonial evidence of the fact of murder. But it is
possible to have circumstantial evidence of the fact of murder; that is to
say, you may find a man dying with a wound upon his head having
exactly the form and character of the wound which is made by an axe,
and, with due care in taking surrounding circumstances into account,
you may conclude with the utmost certainty that the man has been
murdered; that his death is the consequence of a blow inflicted by
another man with that implement. We are very much in the habit of
considering circumstantial evidence as of less value than testimonial
evidence, and it may be that, where the circumstances are not perfectly
clear and intelligible, it is a dangerous and unsafe kind of evidence; but
it must not be forgotten that, in many cases, circumstantial is quite as
conclusive as testimonial evidence, and that, not unfrequently, it is a
great deal weightier than testimonial evidence. For example, take the
case to which I referred just now. The circumstantial evidence may be
better and more convincing than the testimonial evidence; for it may be
impossible, under the conditions that I have defined, to suppose that the
man met his death from any cause but the violent blow of an axe
wielded by another man.